Example of the mesh used for the DSMC simulations in the case where ϕ = 0.65. (a) Full mesh, (b) zoomed-in view, (c) zoom onto the solid surface mesh. The initial mesh is Cartesian and consists of about 100 000 cells. A two-stage local non-conformal refinement is then applied near the solid wall. The refined mesh contains about 2 million cells. The solid surface is described by around 750 000 faces.